Correlation between reliability and oxidation temperature for ultra-dry ultrathin silicon oxide films

Abstract

The correlation between time-dependent dielectric breakdown lifetime and oxidation temperature of 800–950°C for 3.5 and 5.0 nm thick silicon oxide films as gate insulators was investigated. To obtain ideal gate oxide films with few hydrogen-related defects and precise thickness distribution that extremely influence the lifetime, metal-oxide semiconductor diodes with the films used in the evaluation were produced by our continuous ultra-dry process. The films oxidized at 850°C showed the largest lifetimes irrespective of thickness. The enhancement, however, was confirmed only in the diodes selecting the oxidesilicon substrate interfaces as the anode-side, where the lifetime is mainly dominated. Interestingly, a similar relationship was observed in their density characteristics. This suggests that the condition near the oxide-silicon substrate interfaces is probably improved by the 850°C oxidation due to microscopic structural changes.